This invention relates to a signal controller for providing an output signal which is dependent upon the position of a manually settable element, more particularly the present invention is concerned with a linear motion fader having a compact low profile for mounting in a control desk.
Most current linear motion faders for recording studio mixing desks are analogue potential dividers with a ‘tap off’ voltage determined by the position of a manually settable slider and controlling the volume level or amplitude associated with a given channel.
A disadvantage associated with such analogue faders is that, as sound processing moves away from analogue and towards digital processing, the analogue output from existing faders must be converted to a digital signal, thus introducing a further processing step.
WO 97/13121 (and corresponding U.S. Pat. No. 5,719,570 and U.S. Pat. No. 5,986,584) discloses an optical encoder-based fader in which an elongate frame member carries a manually operable linear slider which is slidable longitudinally of the frame member. A taut string or wire is wrapped around pulleys at opposite ends of the frame member and is also connected to the slider so that linear movement of the sliders causes the pulleys to rotate. The pulleys are mounted with their axes of rotation perpendicular to the direction of sliding movement of the slider. One of the pulleys is mounted on the shaft of a rotary optical encoder, whilst the other pulley is mounted on the shaft of a motor which can be used to move the string when it is desired to “replay” a previous editing or mixing sequence. Such an arrangement is not particularly compact in the depthwise direction, particularly at both ends of the fader. Also, simply wrapping the string around the pulleys does not ensure that there a good control over the output of the encoder or a smooth feel to the slider.
As control desk manufacturers make their units smaller and lower, it becomes increasingly difficult to use motorised faders within the required space envelope.